The present invention relates to a pneumatic grinding/polishing machine in which a middle stopper ring serves to effectively isolate the upper inlet port from the lower outlet port with an excellent leakproof effect. Also, a dustproof sheath is used to prevents the splashing dusts from entering the second bearing so as to prolong the using life of the grinding/polishing machine.
FIGS. 1 to 3 show an existing pneumatic grinding/polishing machine which includes a fixed upper casing 11, a lower casing 12, an annular wall 13, an upper and a lower sealing members 14, 15, a rotor 21, multiple vanes 22, a central shaft assembly 23 and a grinding tray assembly 24.
The upper casing 11 is formed with an air inlet 111 connected to an external high pressure air source, an air outlet 112 communicated with atmosphere, a central chamber 113, an inlet passage 114 and an outlet passage 115. The lower casing 12 is secured to the bottom edge of the upper casing 11. The annular wall 13 is formed with an inlet port 131, an outlet port 132 and a rotor receptacle 133. The upper sealing member 14 is disposed with an upper partitioning ring 141 and an upper cover body 142. The lower sealing member 15 is disposed with a lower partitioning ring 151 and a lower cover body 152.
The rotor 21 has multiple equally spaced vane slots 211 for receiving the vanes 22. The central shaft assembly 23 includes a central shaft 231 engaged with the rotor 21, an eccentric block 232 positioned in the lower casing and an eccentric recessed seat having an opening facing downward (not shown). The grinding tray assembly 24 includes a grinding tray shaft 241 and a grinding tray 242 for grinding the surface of a work piece. The rotor 21 is rotatably disposed on the upper and lower sealing members 14, 15 via two bearings, that is, indirectly rotatably disposed on the upper casing 11. Similarly, the grinding tray assembly 24 is rotatably disposed in the recessed seat of the central shaft assembly 23 via another bearing.
After high pressure air is guided into the air inlet 111, the air goes into the inlet port 131 for pushing the vanes 22 so as to rotate the rotor 21. The air is finally exhausted from the air outlet 112 through the outlet port 132. The rotor 21 will drive the central shaft assembly 23 to rotate for driving the eccentric grinding tray 242 to irregularly rotate so as to grind the surface of the work piece.
The conventional pneumatic grinding/polishing machine has some shortcomings as follows:
1. The manufacturing and assembling procedures are troublesome. The conventional pneumatic grinding/polishing machine includes specifically shaped upper and lower partitioning rings 141 and 151. Especially, the upper partitioning ring 141 has two downward extending vertical sections 141A each of which has a toothed portion 141B at its free end. Similarly, the lower partitioning ring 151 has two upward extending lower vertical sections 151A each of which has a corresponding toothed portion 151B at its free end. Therefore, after assembled, the engaged upper and lower vertical sections 141A, 151A can just separate the inlet port 131 and outlet port 132 from each other. It is difficult and time-consuming to manufacture and assemble such elements with vertical sections and toothed portions. Also, the manufacturing cost for such elements is relatively high. PA1 2. The conventional pneumatic grinding/polishing machine is subject to leakage of air. After engaged, a gap will still exist between the toothed portions 141B and 151B. After a period of use, due to high speed rotation of the rotor 21 and the eccentrically irregular rotation of the grinding tray 242, the gap between the toothed portions 141B, 151B will be enlarged. This will lead to leakage of air. PA1 3. Short using life. During grinding, the grinding tray 242 is eccentrically irregularly rotated at high speed. This will make the lower casing 12 fill with irregularly splashed dust. This dust is restricted within the lower casing 12 and tend to be left in the bearing, especially in the second bearing 26 as shown in FIG. 7. Moreover, the bearing itself contains multiple ball members and lubricant so that the dust is apt to attach thereto to damage the bearing or harden the lubricant. This will disable the rotor 21 from smoothly rotating.